Metal Roofing Systems
Learn More About Standing Seam Metal Roofs
Various types of metal roofing systems can be found on both residential and commercial structures. Two common types are standing seam metal roofs and flat lock metal roofs. Metal is also used in flashings, trim, and box gutter liners. Metal systems are recommended by roofing professionals because of their longevity, durability, appearance, resistance to wind, reflectivity, and resistance to fire. Many metal roofs currently in service around the world have been in place for hundreds of years.
Featured Metal Roofing Project: Cabela's @ Liberty Township
The successful installation of a metal roofing system begins with several design considerations, including the following:
- Roof Pitch – Standing seam metal roofs are typically recommended on slopes greater than 3/12. Flat lock roofs are recommended on slopes 3/12 or less.
- Type of Metal – Dissimilar metals can corrode when they come in contact with one another or drain on each other. Also, some metals are naturally weathering while others require painting.
- Thickness of Metal – The gauge or weight of metals must be considered for different types of installations and applications.
- Interior Building Conditions – Vapor barriers or corrosion protection on the underside of the roofing panels must be considered if vapor is able to infiltrate the roof panels.
- Type of Fastener – Rivets, nails, and screws used in metal roofing applications must be compatible with the metal being installed.
- Thermal Movement – Metal, like all building materials, expands and contracts when exposed to changes in temperature. Metal roofs and box gutter liners can fail if the panels are not secured in one direction and able to float in the other.
- Underlayment and Slip Sheets – Combinations of Rosin paper, asphalt felt, and (high temperature) ice and water shield are used to allow the metal panels to expand and contract without tearing the underlayment. The low melting point of the asphalt must also be considered as some metal systems can reach temperatures of 200 degrees Fahrenheit.
After a proper design is specified, a skilled sheet metal foreman will install the metal system. These individuals must be skilled at soldering to successfully install flat lock metal roofs, box gutters, and flashings. Solder is used to fuse metal seams together to ensure that they are water tight. Deer Park Roofing does not recommend the use of caulk as a substitute for solder.
Standing Seam Metal Roofs
Metal standing seam roofs have been gaining popularity as a residential roofing system. These roofs should be installed with concealed fasteners to eliminate the risk of water infiltration at the screw heads. The panels are installed with seam heights of 1 to 2 inches. The seams enable thermal movement within the metal panels, add structural support to the system, and provide a water tight seal. Pre-painted metal panels come in a wide range of color options and can be fabricated from steel or aluminum. Factory applied paint systems will perform much better than field applied paint systems.
Standing seam metal systems can also be designed using copper or galvanized steel. The galvanized steel panels can be designed to replicate the ‘tin roofs’ used in previous centuries. Panels can be fabricated in 10 ft lengths using a break or in custom lengths using a roll former. These roofs are designed to last upwards of 60 years, approximately 3 times as long as asphalt shingle roofing systems.
Flat Lock Metal Roofs
Flat lock roofing systems are fabricated out of copper, galvanized steel, and sometimes stainless steel. These types of roofs are commonly found on cupolas, domes, spires, porches, and low sloped roof areas. Metal panels are fabricated in a sheet metal shop with four interlocking seams, two bent upward and two bent downward. Panels should not be larger than 18 inches by 24 inches and secured to the roof deck with metal clips to prevent thermal movement from damaging the metal or the seams. Flat locked seams must be soldered on all roofs with a slope less than 8/12.
For information about built up gutter systems, box gutters, and/or box gutter liners Click Here.
The following types of metals are commonly used in roofing systems:
Steel is the most common metal used in both residential and commercial roofing because of its strength and cost effectiveness. Steel is a metal alloy that consists of 98% iron and 2% carbon. Steel that is used for metal roofing must be painted or galvanized to prevent it from rusting.
Galvanized steel is coated with a thin layer of zinc. When the zinc coating deteriorates, the roofing components will begin to corrode when exposed to water and oxygen. The rate of corrosion on steel roofs depends on the pitch of the roof, the level of humidity, and the presence of a protective coating. Steep sloped steel roofs will last longer than lower slopes because the water drains faster and the metal dries quicker. Galvanized steel is easily soldered and can be used for almost any flashing detail while pre-painted steel cannot be soldered.
Galvalume is a steel coating that contains both aluminum and zinc. Galvalume out performs galvanized steel in commercial low sloped roof systems. Galvalume cannot be soldered and will corrode if it comes in contact with mortar, making it a poor choice for residential roof systems.
Steel used in roofing applications are most commonly available in thicknesses of 24 gauge (for commercial buildings) and 26 gauge (for residential dwellings). Most building codes require a minimum thickness of 26 gauge steel.
‘Tin Roofs’ are actually made from steel that contains a tin/lead alloy coating. Roofing professionals referred to this type of metal as Terne. Terne metal was easily soldered, durable, and cost effective in comparison to other metal roofing systems. These roofs are commonly found on residential structures in 28 or 30 gauges. Periodic maintenance is required in the form of painting.
Copper Roof systems are known for their durability, longevity, and beauty. Copper sheets used for residential and commercial roofing applications are measured in ounces per square foot instead of thickness. The most common copper weights are 16 and 20 ounces. Copper is easily soldered and requires very little maintenance. Copper is a very soft (malleable) metal and lacks the strength that other metals possess.
Aluminum is a corrosion resistant material that can be used to install standing seam roof systems. Aluminum has a very high rate of thermal expansion and contraction relative to other metals. For this reason, emphasis must be placed on proper design when aluminum is specified on roofing projects. Aluminum used in roofing is pre-painted in a variety of colors. Aluminum coil is measured by its thickness in inches. Common sizes are .019 or .024 inches for residential trim or step flashing and .027 for 5 inch gutters and .032 inches for 6 inch gutters. Commercial roofing specifications typically require .032 or .040 inches for aluminum standing seam roofs or metal copings. Aluminum is very difficult to solder and is not recommended for most flashing details.
For more information about metal roofing systems, please Email Us.